This invention relates generally to agricultural protective fabrics, and more particularly concerns a multilayer protective fabric the characteristics of which dynamically change during the course of a growing season as the result of degradation of one of the fabric layers.
Nonwoven agricultural protective fabrics are used by growers to cover and protect crops, such as vegetables, turf, juvenile citrus trees, ornamental crops, and the like, from the environmental effects of frost, insects, and desiccation. Such protective fabrics not only protect the crops but also produce a greenhouse environment to stimulate and accelerate the growth of many crops. Such nonwoven agricultural protective fabrics must be lightweight, air and water permeable, insulative, able to pass light, and strong enough to avoid tearing as a result of handling and wind.
A number of manufacturers make protective agricultural fabric, including Kimberly-Clark Corporation, the assignee of the present invention. Kimberly-Clark Corporation manufactures and sells a spun-bonded polypropylene fabric having a basis weight of 0.6 ounce per square yard (oz/yd.sup.2) under the trademark Kimberly Farms. Other agricultural protective fabrics include Linktuf agricultural film manufactured by Dow Chemical Company, Midland, Mich. Linktuf film is a rib reinforced low density polyethylene plastic. Another agriculture protective cover is spun-bonded polyester manufactured by The Inter Tech Group, North Charleston, S.C., and sold under the trademark Reemay. Amoco Fabrics and Fiber Co., Richmond, Va., sells a nonwoven polypropylene fabric under the mark Seed Shield. A spun-bonded polypropylene is manufactured by Sodoca SA of France and sold in the United States by International Paper under the trademark Agryl. Beghin-Say SA of France manufactures a polypropylene polyamide extruded film which is sold in the United States under the trademark Agronet by CDK, International.
The nonwoven protective fabrics of the prior art can be engineered to balance the grower's requirement for frost protection, light transmission, air and water permeability, desiccation prevention, and strength in order to meet the particular needs of particular growers. The needs of the grower, however, may change during the course of a single growing season. Obviously, during the early spring when the possibility of frost exists, it is advantageous to have a protective fabric with a high degree of insulation in order to protect young growing plants against freezing. Later in the season once the risk of frost has ended, it is advantageous to have a protective fabric which has a higher degree of air and water permeability as well as a higher degree of light transmission to assist in the growing process. In general, the goals of frost protection and growth enhancement by a protective fabric result in compromise between the need for insulation versus the need for air and water permeability and light transmission over the entire growing season.